I'm building a small project out of 1/4" Baltic birch plywood. I marked up the boards with lumber crayons and then wrote cut marks and part identifications with a pencil. I did most of my sanding with 120 grit to remove the marks and then did a light pass with 150 grit.

It wasn't until I noticed that my once tight-fitting dados were now loose that I realized that I almost sanded through the top layer of the plywood in my efforts to remove the marks.

Are there any non-abrasive, wood-safe ways to remove these marks? If not, how do most woodworkers deal with this on veneered surfaces?

While not an answer to "how do I remove ...", I will say you can buy very soft lead for mechanical pencils, so you get a dark (enough) mark with less force driving pigment into wood, or denting wood.
– donjuedoJun 24 '15 at 20:23

Not an answer as plenty of people have suggested it as a general solution, but as a specific eraser, I would try a "Pentel Hi-Polymer" eraser. I use them for sketching, but they are very soft, EXTREMELY effective, and firm enough to not leave loads of rubber dust everywhere, so I imagine they'd be pretty good for this use too. I don't work for Pentel :)
– WhelkaholismOct 27 '15 at 11:41

Just tried mr clean majic eraser on a project I'm doing. Working great at getting pencil marks and smudges out. Thanks for recommending
– user3243Jan 30 '17 at 19:51

Goo Gone followed by acetone to remove the Goo Gone residue.
– William HirdApr 25 '17 at 4:47

Great.. now I have to keep some tape in my tool box as well.... it's getting heavy enough as it is.
– MattJun 24 '15 at 14:27

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I actually did mark where I thought would be scrap, but then I noticed a dent so I had to reverse the plan... Masking tape would have been a good idea though...
– StevenJun 24 '15 at 14:29

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I would never recommend putting tape on wood that will be stained/finished. Any adhesive left behind will repel stain and finish and you will generally have to use a chemical remover or sanding to get it off
– JamesJun 29 '15 at 16:54

@James I would guess that depends on the tape. Painters tape, as long as it is not left on to long, should remove easy with residue. Can't imagine masking tape would be too bad. The warning you give does stand though
– MattJun 29 '15 at 17:43

@Matt it can certainly work but I have had a few occasions where it caused me some significant rework so I generally avoid it.
– JamesJun 29 '15 at 18:02

It wasn't until I noticed that my once tight-fitting dados were now loose that I realized that I almost sanded through the top layer of the plywood in my efforts to remove the marks.

You're not the first person to do something like this striving to erase layout marks or notes from wood by sanding and you won't be the last. It's the kind of thing that clearly indicates how poorly suited to the task the method is.

Now that I've tried other methods and seen how well they work I would never, under any circumstances, recommend removing pencil marks by sanding.

If it is viable for the removal of wood to be the means to remove layout marks from the surface (i.e. if any reduction in width or thickness is not critical at that stage in the building process) then both planing with a finely-set plane or card scraping would be preferable to sanding.

But it's necessary to have a method that can be used in the many instances when you can't safely pare some wood from the surface, and the best of those in my experience is by wiping with acetone; nothing else even approaches its effectiveness.

I don't know quite how it works but it's something to do with the specific solvent action of acetone and how it interacts with graphite. To use: dampen a corner of a clean rag or a bit of paper towel with the acetone, wipe and pencil marks just vanish.

I've never used acetone on marks left by lumber crayons but it should work on those too. However, I believe they are wax-based so it's likely that just mineral spirits (UK: white spirit) will be effective with those. Another possible method for those posted at bottom.

To be comprehensive I should include other methods that haven't been mentioned in the existing responses:

Common pencil erasers; these can leave a dark smudge on the wood surface just like they can on paper so I can't recommend the method unreservedly, although they can work well.

Putty erasers; these can leave a slight greasy trace on paper and consequently can on wood too so again I have reservations.

Crayon marks:

White bread ball; sound bizarre but it works well to remove normal crayon marks from painted wall, wallpaper and other surfaces. Just rip off a chunk of white bread (avoid crust), form it into a tight ball and rub on the marks and away they go.

Pencil marks - I second the idea of acetone. Not fingernail polish remover because it has oil and perfume and sometimes things like lilac oil. You can buy acetone at any pharmacy.
– jim mcnamaraJun 24 '15 at 17:01

Light planing where the marks are. It has the advantage of targeting where the marks so that you are not actually removing the wood at all. Just the crayon that is sitting above the wood. This should not damage the blade. I read the question again and this might not be an ideal solution for veneer.

Mineral spirits on a rag was is something that I have seen being used. I cannot personally attest for its effectiveness. Much like other solvents proper ventilation is key.

I don't use a pencil where I know a face or portion of the wood will be showing. It usually makes small indentations in the wood.

There was a product out years ago called clean wood and it was made specifically for removing pencil marks from wood prior to staining, it was a liquid that you would pour on the corner of a rag and just wipe a little on the marks and in seconds they would be gone for good, without raising the grain. I used to use this product a lot years ago for trim work especially when the wood was left natural and just a sealer was going to be applied, worked great for me. I don't know if it is still available as I am looking for some right now!!

Did it happen to smell suspiciously like acetone, perchance?
– Charlie KilianApr 21 '17 at 16:10

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Don't mean to be rude, but without actually knowing what the product was, this isn't really an answer to the question. StackExchange is not a forum but rather a Q&A format, so only actual answers are generally accepted. You can comment if you have something like this to add that is not actually an answer.
– StevenApr 21 '17 at 17:23